<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>块级作用域</title>
</head>

<body>
  <script>
    // for (var i = 0; i <= 3; i++) {
    //   console.log(i)
    // }
    // console.log(i)
    if(true){
     let i=20
    }
    console.log(i);
  </script>
</body>

</html>